As student debt continues to grow, getting the best bang for your buck is becoming more important than ever in choosing a college. In response to growing concerns over student debt, 'Best Value' college lists are popping up everywhere.

Graduates sit waiting for commencement exercises to begin during the Florida State University - Panama City graduation at the Marina Civic Center in Panama City, Fla. in 2012. Average student debt among 2012 graduates hit $29,400, according to a recent study.

In the already murky realm of college ratings – in which every campus quality from academic rigor to architecture is boiled down to a number – perhaps no designation is more opaque than the "best value" school. The lists vary widely depending on where you look: U.S. News & World Report's top three "value" colleges are Ivy League schools, and its Top 10 is occupied by superexclusive schools like Stanford and the Massachusetts Institute of Technology. For Forbes, service academies with no tuition, such as West Point and the Naval Academy, come out on top. Other lists use in-state tuition figures, giving high marks to well-regarded, public state schools like the University of Virginia and New College of Florida.

The high variance can be troubling, especially as college students' debt loads continue to grow. Average debt for US 2012 college graduates who took out loans to complete bachelor's degrees hit $29,400 in 2012, according to a study released today by the Project on Student Debt at The Institute for College Access & Success. Seven in 10 college seniors graduated with some debt last year, and more students are taking on riskier private loans as the standards for federal aid tighten up.

Why the disconnect among lists? For one, value is hard to define. "Those rankings are defective for two reasons," Derek Bok, former Harvard University president and author of the book "Higher Education in America," writes via e-mail. "First, students have very different educational needs. A poor student who wants to be an engineer will have very different needs than a rich student who wants to study literature. Second, no one knows how to measure quality – how much students learn at any given college."

As a result, the methodologies for determining such rankings are all over the place. The U.S. News list, released last month, "takes into account a school's academic quality and the 2012-2013 net cost of attendance for a student who receives the average level of need-based financial aid," the release says. "The higher the quality of the program and the lower the cost, the better the deal."

That equation doesn't address accessibility, however. "An Ivy League education's value is purely hypothetical for the 98 percent of [high school] grads who can't get in," Michael McPherson, head of the education-oriented Spencer Foundation in Chicago, writes via e-mail.

While education experts like Mr. Bok and Mr. McPherson put little stock in such lists, the question of value is of paramount importance to many students and families as college costs balloon. In August, the Obama administration set to the task, announcing a set of initiatives aimed at lowering the cost of college and tying federal aid dollars to the value students get for their tuition.

Per the proposal, the Department of Education would develop its own "value ranking" by 2015: a college scorecard that takes into account sticker price, average student debt upon graduation, and the percentage of students receiving Pell Grants – federal scholarships for high-achieving, low-income students – to attend college.

The latter should be a chief concern in determining value, but it's an area in which elite institutions fall short, argues Mark Kantrowitz, vice president and publisher of Edvisors Network, which creates websites about planning and paying for college. "There's a tension between accessibility and reputation," he says.

"The Ivy League as a whole has 11 percent Pell Grant recipients. The rest of the traditional universities have 25 percent [on average]. It's very easy to be generous when you don't have those students."

What's more, prestigious schools with big endowments can be generous with financial aid. Princeton, for instance, has an average debt of $5,096 per student upon graduation. "That's impressive, but it's also partly because they have a relatively wealthy mix of students who can pay tuition and avoid loans altogether," Mr. Kantrowitz adds.

In his view, value rankings should take a college's proportion of low-income, high-risk students into account, to better gauge the value added by the institution – not just its ability to recruit talent. Some lists do: Washington Monthly's "Best Bang for the Buck" list, for example, rewards schools with high graduation rates combined with a low sticker price. (Colleges need to have at least a 20 percent Pell Grant enrollment to qualify.) Amherst College in Massachusetts tops that list. The "Best Bang for the Buck" rankings can be further broken down by national universities, liberal arts colleges, master's universities, and baccalaureate colleges.

But ultimately, the best value-determining system might be more fluid. "Maybe we need a personalized rating that lets you pick your priorities," Kantrowitz says.